1. Field of the Invention
The present invention comprises an apparatus and methods for a human de-amplifier system. In particular, the invention relates to an apparatus and methods for a human de-amplifier system capable of interfacing a human operator and a physical object with miniature dimensions so that the physical object can be dexterously manipulated.
2. Background Art
Teleoperated manipulator has long been developed to perform tasks which would otherwise be performed by humans. Conventionally, a teleoperated manipulator has a separate master-slave system. The human operator, as the master, may be either at a remote location or close to the slave manipulator, but the human is not in direct physical contact with the slave manipulator. The human master can exchange information signals with the slave, but not mechanical power. Therefore, the input signal to the slave is derived from a difference in the control variables (i.e., position, velocity, or other kinetic parameters) between the human master and the slave manipulator, but not from any set of contact forces.
While conventional teleoperated manipulator with the master-slave design is successful in performing many tasks, there are numerous human activities that require human operators performing tasks that demand their intelligence and physical strength often beyond their capability. These tasks cannot be best performed by a traditional robot manipulator because these tasks need a spontaneous information signal and power transfer between the human operator and the working environment, which cannot be provided by the traditional robot manipulator with a master-slave design. Consequently, human extender, a new species of robot manipulator has been developed over the years.
A human extender is a device that amplifies the lifting capacity of a human operator and allows a preselected amount of force feedback to the operator (i.e., the operator can feel part of the load). This type of system is fundamentally different from a teleoperator system because the master and slave manipulators are a single unit in a human extender. This concept was first developed in the 1960's by General Electric during the Hardiman project, as documented in the publications of "Special Interim Study, Hardiman I Prototype Project," Report S-68-1060, General Electric Company, Schenectady, N.Y., Apr. 19, 1968, "Hardiman I Arm Test, Hardiman I Prototype Project," Report S-70-1019, General Electric Company, Schenectady, N.Y., Dec. 31, 1969, and "Final Report on Hardiman I Prototype for Machine Augmentation of Human Strength and Endurance," General Electric Company, Schenectady, N.Y., Aug. 30, 1971. More recently, Kazerooni disclosed a scaled down version of a similar concept in the papers of "Human/Robot Interaction via the Transfer of Power and Information, Part I: Dynamics and Control Analysis," Kazerooni, H., EKE Robotic and Automation Conference, pp. 1632-1640 (Scottsdale, Ariz., 1989), "Human/Robot Interaction via the Transfer of Power and Information, Part 2: An Experimental Analysis," Kazerooni, H., EKE Robotic and Automation Conference, pp. 1641-1647 (Scottsdale, Ariz., 1989), "Human-Robot Interaction via the Transfer of Power and Information Signal," Kazerooni, H., EKE Transaction on Systems, Man, and Cybernetics, Vol. 20, No. 2, pp. 450-463 (1990), and "Human Extenders," Kazerooni, H., J. Guo, Journal of Dynamic Systems, Measurement, and Control, Vol. 115, pp. 281-290 (1990).
The human extender concept is developed in order to take benefit from the strength advantage of robot manipulators and the intellectual advantage of human beings. An important feature of the human extender system is that the input signal to the extender is derived from the set of contact forces between the extender and the human operator. In other words, force reflection occurs naturally in a human extender. Because there is no separate set of actuators, the human hand feels the actual forces on the extender, both direction of motion and a scaled-down version of the load. For example, if a human extender manipulates a 500 lbs. object, the human operator may just feel 10 lbs. while the extender supports the rest of the load. This 10 lbs. contact forces are used not only for manipulation of the object, but also for generating the appropriate signals to the extender controller. The capability of a human extender is often measured by its force reflection ratio, which is defined as the ratio of the real load to the forces the human feels. For the example just given, the force reflection ratio is 50 to 1.
Many potential uses are available for human extender. For example, in an unstructured environment, military personnel often need to use special equipment such as weapon loader to manipulate and orient large objects. An equipment capable of transmitting back to the operator a fraction of the object's dynamics (e.g., its weight, contact forces, slippage, etc.) could significantly enhance productivity, quality, and safety. A human extender can be integrated into a weapon loader to perform such tasks.
Similarly, a human extender can find a wide area of civic use in fields such as the package-delivery service industry. Package-delivery companies, such as United Parcel Service of America, Inc. (UPS), have increased their weight limit on the boxes they carry gradually. UPS has gone from 70 pounds to 150 pounds in order to remain competitive. UPS has also experience a 2 to 3% higher lost time due to injuries than similar types of businesses. A typical job at a UPS hub requires lifting and sorting up to 900 boxes an hour and placing them on a dozen conveyor belts. A dextrous device that has a large work space and can handle large payloads, while utilizing the intelligence of the operator to spontaneously generate the command signal to handle the loads repeatedly, safely, accurately and efficiently, could have a significant impact in the package-delivery service industry. Similar devices can find their use in manufacture assembly lines, in rescue operations, in construction industry and many other areas.
However, a number of problems associated with the available human amplifier systems. Profound instabilities due to gross nonlinearities in the fluid power system (e.g., nonlinear pressure-flow relationship, time varying fluid properties, large quantities of nonlinear friction, time varying system dynamics) and differences in human operator dynamics rendered the system impractical for large force gains as discussed in the paper of "Human-Robot Interaction via the Transfer of Power and Information Signal," Kazerooni, H., EKE Transaction on Systems, Man, and Cybernetics, Vol. 20, No. 2, pp. 450-463 (1990). These instabilities occur when the human extender makes contact with the environment. To overcome these instabilities, a computed torque technique was used with a proportional plus derivative law ("PD") controller as the primary stabilizing controller as disclosed in the paper of "Human Extenders," Kazerooni, H., J. Guo, Journal of Dynamic Systems, Measurement, and Control, Vol. 115, pp. 281-290 (1990). Unfortunately, computed torque technique is a model based scheme that requires significant knowledge about the physical system plus it represents a significant computational burden on the controller. Computed torque can be rendered basically useless if the model is just a few percent off of the calculated value.
A one-axis human amplifier system is described in U.S. Pat. No. 5,865,426 issued to Kazerooni. Upward vertical forces such as gravity and inertia are reduced to the human operator through this system when picking up a load such as a heavy box. The load is attached to a single actuator through a wire rope. Since wire rope can react only to tension type loads this system is suitable for lifting objects only in the upward vertical direction. This system is deficient for tasks that require forces in both the upward and downward directions or if forces and moments are required in other planes of motion.
Moreover, the currently available human extenders are specifically designed for extending the human operator's physical strength to lift more or manipulate large objects. However, in the real world, there are many occasions that manipulating small objects poses challenge to human beings. For example, in performing surgeries including laparoscopic techniques, doctors need to move small physical objects around. In micro assembly of electrical components, such as chip-making manufacture lines, tasks need to be performed on objects with micro dimensions. In modern biotech labs, biological specimens in micro, even nano dimensions need to be manipulated. These activities require human operators to perform tasks that demands their intelligence and well controlled physical strength. However, just as humans cannot move the objects at will beyond their physical strength without help, they often have difficult time to locate, move, or manipulate the objects that can be easily disturbed by a fraction of their physical strength.
Therefore, there is a need to develop a device capable of dexterously manipulating small objects with the dimension in the range of 1 micrometer to 1 mm. Conventional electronically coupled teleoperated systems are incapable of performing such tasks because they have inherent system stiffness. Neither can currently available human extenders deliver satisfactory performance because they have profound instabilities.